Optimal Cross-section Design Research Articles

Subjective approach to optimal cross-sectional design of biodegradable magnesium alloy stent undergoing heterogeneous corrosion

Existing biodegradable Magnesium Alloy Stents (MAS) have several drawbacks, such as high restenosis, hasty degradation, and bulky cross-section, that limit their widespread application in a current clinical practice. To find the optimum stent with the smallest possible cross-section and adequate scaffolding ability, a 3D finite element model of 25 MAS stents of different cross-sectional dimensions were analysed while localized corrosion was underway. For the stent geometric design, a generic sine-wave ring of biodegradable magnesium alloy (AZ31) was selected. Previous studies have shown that the long-term performance of MAS was characterized by two key features: Stent Recoil Percent (SRP) and Stent Radial Stiffness (SRS). In this research, the variation with time of these two features during the corrosion phase was monitored for the 25 stents. To find the optimum profile design of the stent subjectively (without using optimization codes and with much less computational costs), radial recoil was limited to 27 % (corresponding to about 10 % probability of in-stent diameter stenosis after an almost complete degradation) and the stent with the highest radial stiffness was selected.The comparison of the recoil performance of 25 stents during the heterogeneous corrosion phase showed that four stents would satisfy the recoil criterion and among these four, the one having a width of 0.161 mm and a thickness of 0.110 mm, showed a 24 % – 49 % higher radial stiffness at the end of the corrosion phase. Accordingly, this stent, which also showed a 23.28 % mass loss, was selected as the optimum choice and it has a thinner cross-sectional profile than commercially available MAS, which leads to a greater deliverability and lower rates of restenosis.

Integrated assessment of the hydraulic and structural performance of the OBREC device in the Gulf of Naples, Italy

The aim of this work is to analyze the performance of the Overtopping Breakwater for Energy Conversion (OBREC), developed by the team of the University of Campania and installed at prototype scale in the port of Naples. It is a multifunctional coastal structure aimed to protect harbors and produce energy, based on the overtopping principle. This device has been preliminary analyzed by means of experimental and numerical investigations.This contribution provides for the first time an integrated assessment of the OBREC hydraulic and structural performance, by means of the measurements collected at the prototype installation and of numerical modelling i.e. methodologies not affected by the scale effects. The numerical model, developed in the openFOAM environment, is calibrated on the field data gathered during a storm event and is then applied to extend the information related to the OBREC response under the typical wave climate. The results obtained are proposed in terms of overtopping discharge rates and pressures acting along the OBREC profile, under several sea states.Based on these results some recommendations and indications regarding the optimal cross section design are given to maximize the energy production, without compromising the structural stability, and to promote the device exploitability.

Optimal cross-sectional design for minimum embodied energy

In order to reduce the CO 2 emission engineers and architects must optimize the use of materials, particularly steel, making an optimal use of it. It is possible to guarantee the strength of the structural element reducing the amount of steel locating it properly at the cross-section and introducing a higher control level at construction site.

The discussion on optimization models of pure bending beam

This article is devoted to shape optimization design of pure bending beams under single loading condition. Compliance minimization with material volume constraint, the maximum stress minimization problem, and the maximum displacement are considered. In the case of trusses, it has been shown that the former two problems have the same optimal topology. The possibility of extending this result for pure bending beam problems is examined in the present work. First, the comparison of the optimum design results between the maximum displacement, the conventional mean compliance, and the maximum stress is carried out by an example of optimal cross-sectional design of a continuous beam. Then, geometric average displacement (GAD) is introduced in optimization models of linearly elastic structures. The elevated accuracy in results achieved with GAD is shown in this article.

Topology optimization by minimizing the geometric average displacement

On the problem of maximum stiffness design of linear elastic structural topology optimization, the objective of most existing models is to achieve minimum mean compliance. However, in most applications the desired results are ones that achieve minimum maximum displacement. In this article, the comparison of the optimum design results between the maximum displacement and the conventional mean compliance is carried out by an example of optimal cross-sectional design of a continuous beam. The result emphasizes the limitations of the conventional minimum compliance method. An improved index, geometric average displacement (GAD), is introduced in the article for linear elastic structural optimization models, with a GAD-based design model. Several examples are provided to demonstrate the effectiveness of the new proposed formulation.

Cross-Section Designs for the Safety Performance of Buffer-Separated High-Occupancy Vehicle Lanes

This study proposes a methodology to determine the optimal cross-sectional design of a high-occupancy vehicle (HOV) facility for safety performance by evaluating the effects of each relevant design element on safety and tradeoffs among multiple design variables. This aspect of geometric design is critical because it is often difficult to acquire sufficient right-of-way for retrofitting HOV lanes to existing freeway systems with recommended cross-sectional design. Detailed collision data of concurrent-flow buffer-separated HOV lanes, along with their geometric features and traffic flow data, were analyzed to establish collision predictive models by injury types for HOV and the adjacent general-purpose lanes. These models were used to determine the set of cross-sectional design elements that minimizes the expected collision occurrences. As a case study, a real freeway corridor where a conversion from contiguous to buffer-separated types was recently completed was selected to demonstrate the applicability of the proposed method. The evaluation through this case study shows that the proposed methodology is useful in determining the cross-sectional design of HOV facilities for safety based on selective use of available geometric space.

The optimal cross-section design of the “Trapezoid-V” shaped drainage canal of viscous debris flow

Debris flow drainage canal is one of the most widely used engineering measures to prevent and manage debris flow hazards. The shape and the sizes of the cross-section are important parameters when design debris flow drainage canal. Therefore, how to design the appropriate shape and sizes of the cross-section so that the drainage canal can have the optimal drainage capacity is very important and few researched at home and abroad. This study was conducted to analyze the hydraulic condition of a Trapezoid-V shaped drainage canal and optimize its cross-section. By assuming characteristic sizes of the cross-section, the paper deduced the configuration parameter of the cross-section of a Trapezoid-V shaped debris flow drainage canal. By theory analysis, it indicates that the optimal configuration parameter is only related to the side slope coefficient and the bottom transverse slope coefficient. For this study, the Heishui Gully, a first-order tributary of the lower Jinsha River, was used as an example to design the optimal cross-section of the drainage canal of debris flow.

Improved Channel Cross Section with Two-Segment Parabolic Sides and Horizontal Bottom

A channel cross section with parabolic sides and horizontal bottom has been recently published and proved to be more economical (provide lesser construction cost per unit length) than the trapezoidal cross section. This paper presents a new and improved cross section with two-segment parabolic sides and horizontal bottom. Each side of the cross section consists of two parabolic segments smoothly connected. Closed-form relationships for the cross-sectional area and perimeter are developed. For specific parameter conditions, the new cross section produces most of the common cross sections, including the parabolic sides—horizontal bottom and trapezoidal cross sections, as well as new cross-sectional shapes. It provides an additional degree of freedom in determining the optimal cross-sectional design. A spreadsheet-based optimization model for the new cross section that minimizes the total construction cost (excavation and composite linings) is developed. The constraints of the model include channel discharge...